Thermal switch device



June 8, 1943. sc R 2,321,049

THERMAL SWITCH DEVICE Filed April 10, 1940 2 Sheets-Sheet 1 24 r 25 v;- 4 w a Z7 /6 01/5014770/1 I.NVENTOR JOSEPH Scum/amaze ATTORNEYS June 8, 1943. J. SCHMIDINGER THERMAL SWITCH DEVICE 2 Sheets-Sheet 2 Filed April 10, 1940 ASSEMBL Y EXPAND/N6 INVENTOR JOSEPH SCHMlD/NGER it 2mm ATTORNEYS vention Patented June 8, 1943 UNITED STATES PATENT OFFICE THERMAL SWITCH DEVICE Joseph Schmidinger, New York, N. Y.

Application April 10, 1940, Serial No. 328,802

17 Claims.

static switch and mechanism which is char- 1 acterised by its sensitiveness to thermal conditions, by the accuracy with which it may be adjusted to operate under predetermined conditions, by its simplicity in construction and operation, by its reliability and dependability in service under severe service conditions and by the economy with which it may be manufactured.

A further object of the invention is a novel and improved switch and mechanism which is controlled by an expansible wire in response to thermal conditions. I

Further objects of the invention will hereinafter appear.

For a better understanding of the invention reference may be had to the accompanying drawings forming a part of this application wherein:

Figs. 1 to 5 show one embodimentoi' the in- Figs. 6 and 7 show a further modification;

' Figs. 8 and 9 show a further modification;

Figs. 10 11, 12 and 13 show further modifications;

Fig. 14 includes enlarged views illustrating the assembly and theoperation of the switch;'

Figs. 15 and 16 show a further modification of the invention;

Fig.1? shows a further modification of the invention.

Referring to the modification of Figs. 1 to 5 the novel: switch mechanism comprises an insulating mass I, and-in this mass l are mounted a contact carrying arm 2, a contact carrying arm 3, a mount 4 and a post 5. An important feature of the invention is a buckling metallic strip 6 bent about and back upon itself at I and having two substantially parallel legs 8 and 9 whose free ends are fastened as by welding to the pppos ite sides of the mount plate 4. An expansible wire III is fastened at one end to the bend 1 of and is fastened and wrapped around the curved end of the anchor support post 5. The expansible wire may be fastened to the post 5 in any suitable manner, as, for example, by welding and the post 5 may be bent in any suitable manner, as, for example, by the utilization of a tool to put the required tension on the wire III, In the particular embodiment shown the wire I! is continued as a resistor II and electrically connected with the contact arm 2. In this embodiment the leg I is of reduced width as shown at 8' and this reduced part gradually increases in width in both directions until the width is equal to that of the strip. The strip 8 has welded thereto the end of a U-shaped contact l2, this U extending around to the opposite side of the leg 9 to form a contact l2 for co-operation with the contact 3' carried by the contact carrying arm 3. The contact 2' carried by the contact arm 2 contacts with the U l2 at its point of weld to the leg 8.

In the assembly of the switch the expansible wire III is tightened to cause the leg 8 of the strip to buckle away from the contact 2' and to carry the U-shaped contact [2 into engagement with the contact 3'. Upon suitably connecting the wires l3 and I4 and the mount 4 in electric circuits to be controlled the switch is caused to snap from one contact 2 to the other contact 3'. For example, upon connecting the wire I in circuit, the later is heated thereby through v expansion permitting the buckling member 6 to ing up through the disc and being turned over to the buckling strip 6 as, for example, by welding buckle to a position where the leg 8 with its contact member I 2' is in engagement with contact 2'. This operation short circuits the wire H) which thereupon cools and snapsthe contacts 2' and I2 out of engagement with each other as indicated in Fig. 1. .This action is repeated indefinitely. The circuit controlled by the contacts 3' and I2 is at the same time alternately opened and closed with the other circuit.

In the modification of Figs. 6 and 7 the mount 4 for the buckling member Ii is L-shaped and is mounted on an insulating disc [5 with one of the legs 4' of the l member lying flat against the disc. An eyelet contact If is fastened flat against the bottom of the disc l5 and is provided with fingers l6 extending up through the disc andengaging the upper side of the L member 4' for holding the mount, the disc and the contact l6 firmly fastened together. Thetwo other eyelet contacts I! and I8 are similarly fastened to the bottom of the disc I 5 by fingers l1 and II passengage the top of the disc. The contact carrying arms 2 and! are in these instances mounted tion of Figs. 1 to 5 the contacts 2', I are carried on the opposite sides or the buckling member, in the modification of Flgs.6 and 7 these contacts are displaced 'iaterallyof the buckling member 6. The leg 8 of the buckling strip of this modification is also shown of substantially the same width throughout with no reduction in width at any-point.- The expansible wire In is put under tension bymeans of an adjustable pin 23, the latter being adjustably mounted in the mount 4. In order to insulate the wire ID from the pin 3 an insulating bead 24 as, for example, of glass is fastened as, for. example, by fusing to the wire l and the latter continues by the connector or resistor II and is electrically connected with the contact arm 2. The bead 24 is fastened as by fusing to a wire length 25 the wire length being fastened in any suitable manner as by welding to the pin 23. By engaging the end 23' of the pin 23, for example, by any suitable tool, the wire l0 may be put under the desiredtension for operating under the conditions desired. The son'- tact arms 2 and 3 are electrically connected recontact 2' to a point opposite the contact 21 and disposed between planes of the edges of the buckling strip The operation of the modifications of Figs. 8 and 9 is similar to that of the these insulating discs being mounted upon a sleeve 36; and the ends of the legs 8 and 9 of the buckling member 6 are clamped on the opposite sides of the disc 33 while the contact arm 2 is clamped between the discs 34 and 35 and the contact arm 3 between the discs 31 and 32. In the sleeve 35 is journalled the pin 23 for putting the wirelll under tension. The contact arms 2 and 3, and the leg 8 of the buckling strip are provided with openings larger than the sleeve 36 so as'to clear the same and to be insulated therefrom and are extended downwardly to form the electrical connection shown, the contact arm 2 going to an electric load 37 thence to the ground, the contact arm 3 leading by a connection to a'similar electric load 38 and thence to the ground andthe leg 8 leading to the opposite side of the. electric circuit. The operation is similar to the operation with respect to the modification of Figs. 1 to 5. The switch mechanism of this modification of Figs'lii and 11 may be mounted in any suitable manner, as, for example, upon an insulating .disc like the disc i5 of Figs. 6 and '7.

Figs. Band 13 show a means for mounting the mechanism shown in Figs. 10 and 11. comprises an insulating disc with the lower end of the contact arm 2 being formed with an angle piece 39 which .is' clamped in position by the .turned over fingers 15.

through the disc from a contact 16. The lower end of theleg 8 is, provided preferably integrally passing upwardly In the embodiment of'Figs. l5 and 16 the leg 8 is provided with a contact member 42 which is riveted in an opening formed therein, this contact 42 being extended into a contact 42" for engagement with the contact 3'. This simplifies the construction and mount of the contacts, the contact 2 co-operating and contacting with the contact face 42 and the contact 3' (Jo-operating and contacting with the contact 42'.

In the embodiment of Fig. 17 the buckling strip which is formed of two separate legs 8 and 9 are rigidly fastened and clamped together at their upper ends by means oi the rivet 43 and insulating washers 44 shown. The wire H1 is fastened at its upper end to this rivet 43. The lower ends of the legs 8 and 3 are clamped between three insulating discs or members 44, 45 and 46 which are in turn clamped together by the rivet member 47. The legs 8 and 9 of the buckling strip are provided with openings larger than the rivet 41 so as to clear the same and to be insulated therefrom. The upper end of .the leg 9 is also provided with an opening larger than the rivet 43 so as to clear the same and be insulated therefrom. The upper end of the leg 8 however is in electrical contact with the rivet 43. There is also clamped against the insulating disc or member 46 a metallic plate member 48 whichiorms an electrical connection with an electrical load 49 which is connected on the other side of the ground. The plate member 48 is a fastening and tightening lug 50 formed thereon with which the wire 10 is fastened, as, for example, by electrical welding. The wire l0 may be put under tension by bending the ing 58. The leg 9 of the buckling strip is extended downwardly to connect with the other side of the circuit. The two legs 3 and 9 carry contacts 5| which when the wire it! is cooled are in engagement. Upon connecting the mechanism in circuit the wire I0, being in series through the contacts Si, is heated up and, accordingly, upon the extension thereof the circuit is broken at the contacts 5!. Upon a breaking of the circuit the wire again cools to permit the closing of the contacts at 5| and this operation is repeated.

Fig. 14 is an enlarged view of the buckling strip and mount showing the assembly and the operation thereo mate relation of the parts before the wire I0 is put under tension. 141) shows the wire In being tensioned by adjusting the pin 23 and it is observed that the first tension operation results in.

caused to snap over to the right out of engagement with the contact 2'. In this adjusting and tensioning operation the contact 2' is also ad- ThiS - sion thereof.

justed relatively to the strip so as to obtain the required operating actions desired. Figs. 14d and 14e illustrate the operation upon the heating of the wire ill, the arrows showing the expanthe first expansion of the wire 10 due to heating results in the upper end of the buckling strip 6 therewith-with a tongue 40 for connecting-with the. fingers .l-l' of the eyelet contact l1 and' the lower end of contact arm 3 is provided with a similar tongue 4! which is electrically connected with the fingers l8 of the eyelet contact 18;

moving slightly to the right or resulting in a force tending to move it to the right, as indicated by the small arrow at the top of Md. The further heating of the'wire I0 results in the snapping over of the contact l2 into contact with contact 2' as shown in [4a.

14a illustrates the approxi Starting with the positionindicated in Me and with the closure of the circuit,

action in either event.

although certain of the advantages of the invention may be obtained by different relative arrangements of the double strip 6 and the wire It, the preferred arrangement is that. shown wherein the wire II is disposed at a relatively small and acute angle to the strip 6. With the arrangement shown the member 8 when it is biased by the tensioning of the wire III is put under compression by the act of the wire pulling the free end of themember towards the side on which the wire 18 is disposed; This compression of the leg 8 results in a tendency of it to buckle in the direction of the pull of the wire. If there is a stop or contact present, as for example like the contact 2', to check the buckling action, this initial movement and compression of the leg 8 simply results in greater pressure upon the contact being exerted both by the pull of the free end of the double strip in that direction and by the outward buckling action of the leg. If

there is no stop, as for example illustrated in Fig. 17, then the action is as follows: Assuming the wire ll! of Fig. 17 to be extended and with the two legs 8 and 9 under no restraint by the wire, and with the contacts 5| separated, the first initial movement of the upper end of the double strip upon the cooling of the wire I!) is-to cause the leg 8 to. buckle slightly outwardly from the leg 9. This condition is only momentary, however, because immediately upon further movement of the free end in that direction'due to the further cooling of the wire Hi the leg 8 is caused to buckle in the opposite direction to close the contacts 5| as shown in Fig. 17. Accordingly, whether it is a contact closing action upon cooling of the wire 10, as shown in Fig. 17, or a contact opening action, as shown in Fig. 14, the action is a snap This snap action is not only present where the leg on the side of the pull (leg 8) when not under restraint by the wire is straight but also where it may have some convexity toward the pull wires. Convexity of this leg away from' the pull wire when not under restraint by the latter tends to minimize or prevent snap action.

The doublebuckling strip or member 6 containing the closely disposed legs 8 and 9 together with the expansible wire In possesses a number of advantages in thermal switch mechanisms. It

is capable of the strong snap switch action desired in practice, it may be adjusted for either high or low speed contact action, it can be made in very small dimensions, so as to be accommodated in restricted spaces or chambers, it is particularly suitable for glass press mountings and it maybe used as a flasher, a time switch, a relay and a circuit breaker.

.1. A'thermal switch, mechanism comprising a support, a double spring strip having the members thereof disposed face to faceand firmly anchored at one end to said support and rigidly hot.

for putting one of the members under buckling constraint when the free end is moved relatively to the support, said strip carrying a contact, wire fastened to'the free end of said double strip and biasing the same to occupy one position when the wire is relatively cool and another pomtion when the wire is relatively hot with one of the members serving as a stop for the other in one position, at least one of the members of the double strip carrying a contact. 7 I

B. A thermal switch mechanism comprising a support, a double spring strip having the members thereof disposed face to face and firmly anchored at on end to said support and rigidly fastened at the other and free end to each other for putting one of the members under buckling constraint when the free end is moved relatively to the support, said strip carrying a contact, wire fastened to the free end of said double strip and biasing'the same to put one of the members of the double strip under buckling compression and a contact carried by said last named member.

4. A-thermal switch mechanism comprising a a double buckling strip whose members are disposed closely together and face to face and are rigidly fastened at one end against movement with the other ends of the double strip rigidly fastened against relative movement thereof and an expansible wire rigidly fastened to the free end of said buckling strip and disposed at an acute angle thereto, said expansible wire biasing said strip to occupy one position when the wire is relatively cool and another position when the wire is relatively hot and a contact carried by said double strip.

5. A thermal switch mechanism comprising a support, a buckling strip bent into sharp U -form to form a double buckling strip with the legs thereof disposed closely together and face to face and their ends rigidly fastened to said support and having said sharp U-bend free to move in a direction at right angles to the plane of the strip for putting one of the legs under buckling constraint and an expansible wire rigidly fastened to the U member at a point adjacent the free end thereof, said wire biasing the U member to occupy one position when the wire is relatively cool and another position when the wire is relatively two separate strips which are closely disposed to fastened at the other and free end to each other for putting one of the members, under buckling constraint when the freeend is moved relatively to the support, said strip carrying a contact, and I an expansible wire fastened'at the free end of said support, a double spring strip having the members thereof disposed face to face and firmly anchored atone end to said support and rigidly fastened at the other and free end to each other I constraint when the free end is moved relativelyeach other and face to face and are rigidly fasa tened to the frame member at one end and having their other ends rigidly fastened together at their free ends for putting one of the strips under buckling constraint when the free end is moved relatively to the frame, and an expansible wire fastened to the free end of said buckling strip and biasing the-same to one position when the wire is relatively cool and to another position when the wire is relatively hot, and a contact carried by one of the members of said double' strip.

7. A thermal switch mechanism comprising a support, a double spring strip having the members thereof disposed face to face and firmly anchored at one end to said support and rigidly v fastened at the other and free end to each other for putting one of the members under buckling to the support. said strip carrying acontact, and an expansible wire fastened at the free 'end of said spring strip and biasing said strip to occupy one position when the wire is relatively cool, and another position'when the wire is relatively hot, one

'of the members of the double strip being reduced in width intermediate its ends.

8. A thermal switch mechanism comprising a support, a double spring strip having the-members thereof disposed face to face and firmly anchored at one end to said support and rigidly fastened at the other and free end to each other for putting one of the members under buckling constraint when the free end is moved relatively to the support, said strip carrying a contact, and an expansible 'wire fastened at the free end of said spring strip and biasing said strip to occupy one position when the wire is relatively cool and another position when the wire is relatively hot, one

of the members of the double strip being reduced in widthintermediate its ends and being provided with a U-shaped contact member.

' chored at one end to said support and rigidly fastened at the other and free end to each other for puttin one of the members under buckling constraint when the free end is moved relatively to the support, said strip carrying a contact, and an expansible wire fastened at the free end of said spring strip and biasing said strip to occupy one position when the wire is relatively cool and another position when the wire is relatively hot, said contact members being mounted in an insulating press.

10. A thermal switch mechanism comprising a support, a double spring strip having the members thereof disposed face to face and firmly anchored at one end to said support and rigidly fastened at the other and free end to each other for putting one of the members under buckling constraint when the free end is moved relatively to the support, said strip carrying a contact, and an expansible wire fastened at the free end of said spring strip and biasing said strip to'occupy one position when the wire is relatively cool and another position when the wire is relatively hot, comprising an insulating press and contact supports, with-the contact supports and the double strip mounted. in said insulatin press.

11. A thermal switch mechanism comprising a support, a double spring strip having the members thereof disposed face to face and firmly anspring strip and biasing said strip to occupy one position when the wire is relatively cool and another position when the wire is relatively hot, the double strip being mounted on a support carried by an insulating disc.

12. A thermal switch mechanism comprising a double buckling strip with the members thereof disposed face to face and carrying a contact and mounted rigidly at one end against movement with the other ends of the double strip rigidly fastened against relative movement thereof, and an expansible wire fastened at the free' end of said buckling strip and biasing said strip to occupy one position when the wire is relatively cool and another position when the wire is relatively hot, a stationary contact member, an insulating sleeve structure and a tensiom'ng pin journaled in said structure, said stationary contact member 13. A thermal switch mechanism of the char- I acter set forth comprising a support, a double buckling strip anchored at one end to said support and having the members thereof 'disposed face to face and rigidly fastened at .the other and free end to each other for putting one of the members under buckling constraint when the free end is moved relatively to the support, an expansible wire fastened to the buckling strip at,

the free end and means for tensioning said wire,

' and a contact carried by one of the members of said. buckling strip at a point intermediate its ends.

14. A thermal. switch mechanism comprising a double bucklin strip whose members are disposed closely together and face to face and are rigidly fastened at one end against movement with the other ends of the double strip rigidly fastened against relative movement thereof and an expansible wire rigidly fastened to the free end of said buckling strip and disposed at an acute angle thereto, said expansible wire biasing said strip to occupy one position when the wire is relatively cool and another position when the wire is relatively hot and a contact carried by said double strip, one of the members of the double buckling strip having greater buckling action than the other and said wire being disposed at the side of'said member.

15. A thermal'switch mechanism comprising a support, a double spring strip carrying a contact and anchored atone end to said support, with the other end of the double stripfree to move relatively to the support and in a direction at right angles to the plane of the strip, the members of the doublestrip being disposed closely together and face to face and being rigidly fastened to each other at the free end for 'setting up buckling stresses in one of the members by move- .ment of the free end toward the side of that member, and thermally responsive means engaging said strip and controlling the same.

16. A thermal switch mechanism comprising a. support, adouble buckling strip of duplicate structure rigidly mounted at one end on said sup- .port with the other end free to move relatively to the support and with the members thereof disposed closely together and face to face, the adjacent ends of said members being rigidly fastened together against relative movements and one of said members being thereby put under buckling longitudinal stress when the free end of the double strip is moved, and thermally actuated means engaging said strip at the free end and moving the same to apply a buckling and snap action to one of said members.

17. A thermal switch mechanism comprisinga support, a double bucklingstrip of duplicate structure rigidly mounted at one end on said support with the ,other end free to move relatively to the support and with the members thereof disposed closely together and face to face, the adjacent ends of said members being rigidly fastened against relative movements and one of said members being thereby put under buckling longitudinal stress when the free end of the double strip is moved, and means'engaging said double- 

